1. Field of the Invention
The present invention relates generally to frames that support glazings, and more specifically, relates to a method and apparatus for an improved system for supporting a glazing.
2. Description of the Related Art
In an increasingly violent society, businesses and homes are subject to an increased number of threats against both life and property. These threats to life and property can include ballistic threats, threats of explosive blasts, forced entry threats, and others.
Businesses and homes in areas of high crime are increasingly forced to employ security measures to protect against these threats. These security measures include the installation of glazings with increased strength. For example, bullet resistant glazings or glazings that can resist certain explosive blast threats are finding their way into both residential and industrial buildings.
Additionally, buildings in areas that are subject to natural disaster, such as hurricanes, tornadoes and severe storms, require weatherproofing and additional protection from the elements.
Unfortunately, conventional security improvement schemes require that the existing window and frame be removed and replaced with a new glazing unit and a new frame. Because the old windows and frames need to be removed first before the new windows and frames can be installed, the costs of such a job are greatly increased. Moreover, the area downtime, that is, the time required for workmen to come in, tear down the existing structure, and install the new structure, is also substantial. Furthermore, there is a risk of contamination to the work-area resulting from the demolition and reconstruction of the frame and surrounding building structure.
Another disadvantage of conventional schemes is that the noise, commotion and disruption inherent in tearing out the old frame and existing building materials, in addition to the significant down-time, precludes a discreet security enhancement. Because of the conspicuous nature of conventional schemes, they may unnecessarily cause fear in the workplace or unwittingly reveal to third parties the additional security measures.
Also, the conventional technique for increasing the security of a building is time-consuming and costly, requiring substantial lead time for pre-fabrication of the new frame prior to installation.
Furthermore, conventional retrofit methods for increasing the security of a building cannot be aesthetically finished and leave unsightly anchoring, such as screws or other evidence of sizing the frame (e.g., cut marks, edges, scratches). Once the new window glazing is in place, conventional frames do not allow for upgrades to glazings with a greater thickness. In order to upgrade with conventional frames, the entire frame must be removed and a suitable frame having dimensions to accommodate the glazing having a greater thickness must be installed.
Another disadvantage is that conventional frames and methods to install them are costly, time-consuming, and require two or more workers to aid in positioning the glass or glazing in the frames.
Conventional frames are not designed to withstand both the positive phase and negative phase of an explosive detonation (explosion). The positive phase of an explosion is characterized by highly compressed air traveling radially outward from the source of the explosion at supersonic velocities. The negative phase of an explosion is characterized by the shockwave falling below surrounding atmospheric pressure creating suction. Behind the shockwave, a vacuum is created and air rushes in to fill the vacuum creating high intensity wind or drag pressure on the surfaces of buildings and other structures.
A well known standard for grading the blast resistant quality of a window system is the Protection Level ratings established by the Government Services Administration (GSA) for federal facilities. Based upon reproducible tests performed by the U.S. Army Corps of Engineers, Table I identifies the ratings and security criteria of the GSA. These levels of protection are for positive over blast pressure only, and do not account for fragmentation and/or shrapnel impacts.
TABLE IPerformance/Description of Window GlazingProtection LevelCondition1 - SafeGlazing does not break. No visibledamage to glazing or frame.2 - Very HighGlazing cracks, but is retained bythe frame. Dusting or very smallfragments near sill or on flooracceptable.3a - HighGlazing cracks. Fragments enterspace and land on floor no furtherthan 3.3 feet from the window.3b - HighGlazing cracks. Fragments enterspace and land on floor no furtherthan 10 feet from the window.4 - MediumGlazing cracks. Fragments enterspace and land on floor and impacta vertical witness panel at adistance of no more than 10 feetfrom the window at a height nogreater than 2 feet above thefloor.5 - LowGlazing cracks and window systemfails catastrophically. Fragmentsenter space, impacting a verticalwitness panel at a distance of nomore than 10 feet from the windowat a height greater than 2 feetabove the floor.
Accordingly, there remains a need in the industry for an improved window system and a method of installing the improved window system that overcomes the disadvantages set forth above.